REPAIR OF ADVANCED GAS TURBINE PARTS

GE Frame 6 gas turbine is considered an advance heavy-duty turbine. The unit was originally developed as a replacement for the 24 MW FR-5001 series. The dimensions are approximately the same as FR-5001 but with 40 percent higher output and 10 percent increase in thermal efficiency. This performance improvement was realized by increased compression ratios, use of new coatings for hot section components and extensive cooling technology. The first turbine was put into operation around 1980. (1) In 1989 a Frame 6 turbine of a power station was due for major overhaul. This turbine had accumulated 24000 operation hours, using natural gas as fuel When the parts were removed, it was revealed that the stg. 1 rotor blades and first stage nozzle were severely damaged, such that they could not be reinstalled. The high cost of new replacement and long deliveries for such parts encouraged the end user to search for alternatives. Repair of turbine hot section parts is an established and well proven technique, although at that time, no one did any major repairs on these parts. To ensure that the repaired parts met the operation requirements, a close liaison was established between the end user's technical staff, an independent inspection authority and the repair shop engineers.